Exchange 2010 DAG–Collapse the MAPI networks in a DAG

To avoid DAG switchover issues, you should always collapse the MAPI networks in a DAG.

The following Technet article state that we “should” or we “must” do it:

http://technet.microsoft.com/en-us/library/dd298065.aspx#Dat

http://technet.microsoft.com/en-us/library/dd638104.aspx#NR

… and Tim McMichael explains why :

http://blogs.technet.com/b/timmcmic/archive/2011/09/26/exchange-2010-collapsing-dag-networks.aspx